Try to unscrew the roof, if it doesn't feel like the screw is raising up - stop turning as the shaft it is screwed to is also turning and this will twist the roof lights power wire inside the central shaft and rip the connection off the land on the circuit board below. This will also stop the motor supply. If you gently insert a wedge between the outer rim of the roof (push in that side's retaining tab), you can insert a pair of long nose pliers in and grip the central shaft, then you unscrew the top screw and remove the roof. Now you can look for broken wires.